Significant Figures Calculator
Count the significant figures in a number, see which digits count, and round to any number of significant figures.
significant not significant ambiguous
Counting rules
Every non-zero digit counts, and so do zeros between them (the middle zero in 4050). Leading zeros only place the decimal point and do not count (0.004). Trailing zeros after a decimal point count (2.50 has three). Trailing zeros in a whole number without a decimal point are ambiguous, so measured values are best written in scientific notation.
Frequently asked questions
How many significant figures does 0.004050 have?
Four: 4, 0, 5 and the final 0. The leading zeros only place the decimal point, while the zero between 4 and 5 and the trailing zero after the decimal point both count.
Does 1200 have two or four significant figures?
It is ambiguous. Without a decimal point the trailing zeros may just be placeholders, so it could be 2, 3 or 4. Write 1.2 × 10³, 1.20 × 10³ or 1.200 × 10³ to make it clear.